Longitudinal hematological change in uncomplicated twin pregnancies: The white blood cell count decreases through pregnancy after the first trimester.

OBJECTIVE: Longitudinal hematological changes throughout twin pregnancies have not been reported. This study aimed to reveal longitudinal changes in hematological indices in twin pregnancies. MATERIALS AND METHODS: We conducted a retrospective chart review of hematological changes in uncomplicated twin pregnancies delivered at ≥37 weeks of gestation between 2010 and 2013 and randomly selected uncomplicated singletons during the same period. A complete blood count and hemogram were performed as blood examinations in the first trimester (9-13 weeks), late second trimester (22-27 weeks), mid-third trimester (33-35 weeks, only in twin pregnancies), and late third trimester (36-38 weeks). We evaluated inter-trimester differences in hematological indices and compared the values between twin and singleton pregnancies in each trimester. RESULTS: The final analysis group included 60 twin pregnancies and 63 singleton pregnancies. The white blood cell (WBC) count in twin pregnancies decreased throughout the pregnancy after the first trimester and became significantly lower than that in singletons in the late third trimester. The WBC count showed only a slight decrease in the third trimester in singleton pregnancies, whereas it showed a marked decrease throughout the pregnancy in twin pregnancies. The marked decrease in the total WBC count in twin pregnancies is mainly due to a decrease in neutrophils. The red blood cell count and hemoglobin and hematocrit values in twin pregnancies showed more marked decreases in the second trimester than in singletons. No decrease was observed after the second trimester of pregnancy. The platelet count decreased in the third trimester of twin pregnancies. CONCLUSION: We clarified the longitudinal hematological changes in twin pregnancies that showed augmentation of or differed from those of singleton pregnancies. It should be specifically mentioned that the WBC count markedly decreased through pregnancy after the first trimester, which is a characteristic change in twin pregnancies.

[Association between maternal plasma one-carbon biomarkers during pregnancy and fetal growth in twin pregnancies].

Objective: To characterize the relationship between the levels of plasma methyl donor and related metabolites (including choline, betaine, methionine, dimethylglycine and homocysteine) and fetal growth in twin pregnancies. Methods: A hospital-based cohort study was used to collect clinical data of 92 pregnant women with twin pregnancies and their fetuses who were admitted to Peking University Third Hospital from March 2017 to January 2018. Fasting blood was collected from the pregnant women with twin pregnancies (median gestational age: 18.9 weeks). The levels of methyl donors and related metabolites in plasma were quantitatively analyzed by high-performance liquid chromatography combined with mass spectrometry. The generalized estimation equation was used to analyze the relationship between maternal plasma methyl donors and related metabolites levels and neonatal outcomes of twins, and the generalized additive mixed model was used to analyze the relationship between maternal plasma methyl donors and related metabolites levels and fetal growth ultrasound indicators. Results: (1) General clinical data: of the 92 women with twin pregnancies, 66 cases (72%) were dichorionic diamniotic (DCDA) twin pregnancies, and 26 cases (28%) were monochorionic diamniotic (MCDA) twin pregnancies. The comparison of the levels of five plasma methyl donors and related metabolites in twin pregnancies with different basic characteristics showed that the median levels of plasma choline and betaine in pregnant women ≥35 years old were higher than those in pregnant women <35 years old, and the differences were statistically significant (all P<0.05). (2) Correlation between plasma methyl donor and related metabolites levels and neonatal growth indicators: after adjusting for confounding factors, plasma homocysteine level in pregnant women with twins was significantly negatively correlated with neonatal birth weight (ß=-47.9, 95%CI:-94.3- -1.6; P=0.043). Elevated methionine level was significantly associated with decreased risks of small for gestational age infants (SGA; OR=0.5, 95%CI: 0.3-0.9; P=0.021) and low birth weight infants (OR=0.6, 95%CI: 0.4-0.9; P=0.020). Increased homocysteine level was associated with increased risks of SGA (OR=1.5, 95%CI: 1.0-2.2; P=0.029) and inconsistent growth in twin fetuses (OR=1.9, 95%CI: 1.0-3.7; P=0.049). (3) Correlation between the levels of plasma methyl donors and related metabolites and intrauterine growth indicators of twins pregnancies: for every 1 standard deviation increase in plasma choline level in pregnant women with twin pregnancies, fetal head circumference, abdominal circumference, femoral length and estimated fetal weight in the second trimester increased by 1.9 mm, 2.6 mm, 0.5 mm and 20.1 g, respectively, and biparietal diameter, abdominal circumference and estimated fetal weight increased by 0.7 mm, 3.0 mm and 38.4 g in the third trimester, respectively, and the differences were statistically significant (all P<0.05). (4) Relationship between plasma methyl donor and related metabolites levels in pregnant women with different chorionicity and neonatal birth weight and length: the negative correlation between plasma homocysteine level and neonatal birth weight was mainly found in DCDA twin pregnancy (ß=-65.9, 95%CI:-110.6- -21.1; P=0.004). The levels of choline, betaine and dimethylglycine in plasma of MCDA twin pregnancy were significantly correlated with the birth weight and length of newborns (all P<0.05). Conclusion: Homocysteine level is associated with low birth weight in twins, methionine is associated with decreased risk of SGA, and choline is associated with fetal growth in the second and third trimesters of pregnancy.

[Effects of gestational weight on the association between serum high sensitivity C reaction protein and gestational diabetes mellitus among twin gestations: A cohort study].

OBJECTIVE: To investigate the association between serum high sensitivity C-reaction protein (hsCRP) in early pregnancy and gestational diabetes mellitus (GDM) among twin pregnant women, and to explore the effects of the pre-pregnant body mass index (BMI) and gestational weight gain (GWG) status on such association. METHODS: Twin pregnant women with pre-pregnant BMI greater than or equal to 18.5 kg/m2 were recruited at Department of Obstetrics and Gynecology of Peking University Third Hospital from March 2017 to December 2020. Serum samples collected in early pregnancy were analyzed for hsCRP using particle-enhanced immunoturbidimetric method. In the following visits, the information about GWG and GDM were prospectively collected in every trimester. The association effect between hsCRP tertiles and GDM were estimated using Logistic regression, and further converted into risk ratio (RR). Cochran-Mantel-Haenszel test and mediation analysis were used to explore the effects of BMI and GWG status on the association. RESULTS: Among the included 570 twin pregnant women, 31.6% deve-loped GDM, 26.1% were pre-pregnant overweight or obesity, and 49.5% with GWG out of referenced range. After adjustment for confounding factors, risk of developing GDM in twin gestations with the middle tertile and highest tertile of serum hsCRP in early pregnancy were 1.42 fold (95%CI: 1.02-1.89) and 1.54 fold (95%CI: 1.12-2.02), respectively, compared with the lowest tertile of serum hsCRP, and there existed significantly linear trend (P=0.022). Findings from mediation analysis illustrated that pre-pregnant BMI had partial mediating effect on the association, and BMI accounted for 23.84% (P < 0.001) of the increasing GDM risks with elevated hsCRP. Joint analysis with hsCRP and GWG found that those who were with GWG out of referenced range accompanied with the higher hsCRP tertiles (>1.21 mg/L) had significantly 2.31 fold increased risk according to those who were with GWG in the referenced range accompanied with the lowest hsCRP tertile (≤1.21 mg/L, P < 0.01). CONCLUSION: Elevated hsCRP in early pregnancy significantly increased GDM risk among twin pregnant women. The hsCRP-GDM association was dependent on GWG status, and pre-pregnant BMI had partial mediating effect on such association. It is suggested that twin pregnant women should consider systemic inflammation and gestational weight at the same time to reduce GDM risk.

Twin-to-twin transfusion syndrome complicated with in utero limb ischemia of the donor twin - a case report.

BACKGROUND: In utero limb ischemia is a rare complication of the monochorionic twin pregnancies complicated with twin to twin transfusion syndrome (TTTS). The condition is more often seen in recipient twins. There are few theories of the pathogenesis including in utero venous thromboembolism, but the cause remains unclear. However, limb ischemia is thought to be unrelated with any prenatal intervention. CASE PRESENTATION: We present a case of a monochorionic twin pregnancy complicated with TTTS admitted to the Clinic for selective fetoscopic laser photocoagulation. The invasive procedure failed due to poor visibility. In the following weeks of pregnancy, amnioreduction procedures were performed. At 28 weeks of gestation due to twin anemia-polycythemia sequence diagnosis the patient was qualified for cesarean section. Postnatally, the donor twin was diagnosed with lower right limb ischemic necrosis. The extremity was amputated 2 days later with an uncomplicated recovery. After speculations of the potential pathogeneses it was suggested that the ischemic limb occurred as a complication of the main condition - TTTS. CONCLUSIONS: In literature, there have been no cases reported of TTTS stage I complicated with donor twin limb ischemia. The actual cause of the in utero limb ischemic necrosis in monochorionic twins remains unknown. Nevertheless, increased attention to the potential complication after failed invasive procedures or conservative treatment should be required.

Effects of gestational weight on the association between serum high sensitivity C reaction protein and gestational diabetes mellitus among twin gestations: A cohort study / 北京大学学报(医学版)

OBJECTIVE@#To investigate the association between serum high sensitivity C-reaction protein (hsCRP) in early pregnancy and gestational diabetes mellitus (GDM) among twin pregnant women, and to explore the effects of the pre-pregnant body mass index (BMI) and gestational weight gain (GWG) status on such association.@*METHODS@#Twin pregnant women with pre-pregnant BMI greater than or equal to 18.5 kg/m2 were recruited at Department of Obstetrics and Gynecology of Peking University Third Hospital from March 2017 to December 2020. Serum samples collected in early pregnancy were analyzed for hsCRP using particle-enhanced immunoturbidimetric method. In the following visits, the information about GWG and GDM were prospectively collected in every trimester. The association effect between hsCRP tertiles and GDM were estimated using Logistic regression, and further converted into risk ratio (RR). Cochran-Mantel-Haenszel test and mediation analysis were used to explore the effects of BMI and GWG status on the association.@*RESULTS@#Among the included 570 twin pregnant women, 31.6% deve-loped GDM, 26.1% were pre-pregnant overweight or obesity, and 49.5% with GWG out of referenced range. After adjustment for confounding factors, risk of developing GDM in twin gestations with the middle tertile and highest tertile of serum hsCRP in early pregnancy were 1.42 fold (95%CI: 1.02-1.89) and 1.54 fold (95%CI: 1.12-2.02), respectively, compared with the lowest tertile of serum hsCRP, and there existed significantly linear trend (P=0.022). Findings from mediation analysis illustrated that pre-pregnant BMI had partial mediating effect on the association, and BMI accounted for 23.84% (P < 0.001) of the increasing GDM risks with elevated hsCRP. Joint analysis with hsCRP and GWG found that those who were with GWG out of referenced range accompanied with the higher hsCRP tertiles (>1.21 mg/L) had significantly 2.31 fold increased risk according to those who were with GWG in the referenced range accompanied with the lowest hsCRP tertile (≤1.21 mg/L, P < 0.01).@*CONCLUSION@#Elevated hsCRP in early pregnancy significantly increased GDM risk among twin pregnant women. The hsCRP-GDM association was dependent on GWG status, and pre-pregnant BMI had partial mediating effect on such association. It is suggested that twin pregnant women should consider systemic inflammation and gestational weight at the same time to reduce GDM risk.

Predictive value of the sFlt-1/PlGF ratio for preeclampsia in twin pregnancies: a retrospective study.

Objective: This study aimed to investigate the efficiency of the soluble Fms-like tyrosine kinase 1 (sFlt-1)/placental growth factor (PlGF) ratio in predicting preeclampsia (PE) within 4 weeks in twin pregnancies.Methods: Seventy-eight women with serum angiogenic markers measured at 28 + 0 to 30 + 6 weeks of gestation were enrolled. A receiver-operating characteristic curve was used to determine the sFlt-1/PlGF ratio threshold to predict PE.Results: A cutoff value for the sFlt-1/PlGF ratio of 22.2 predicted PE presence within 4 weeks.Conclusion: An sFlt-1/PlGF ratio of ≤22.2 is potentially indicative of PE absence within 4 weeks in twin pregnancies.

Establishment of reference intervals of complete blood count for twin pregnancy.

BACKGROUND: Twin pregnancy poses a high risk, and its incidence has increased in recent years. Establishment of reference intervals of complete blood count (CBC) for women with twin pregnancies during pregnancy may aid in the prognosis of adverse outcomes. METHODS: The incidence of complications and the intensity associated with adverse outcomes were analyzed in 1153 cases of twin pregnancy. A total of 253 cases in the twin pregnancy reference cohort were screened from all candidates after complications and adverse pregnancy outcomes were excluded. Complete blood count data were collected during the mid- and late-term of pregnancy and analyzed using SPSS to establish the reference intervals for peripheral blood in twin pregnancy. RESULTS: Premature rupture of the membrane and pelvic inflammatory disease were highly positively correlated with adverse outcomes, with OR values of 3.31 and 3.81, respectively. Within the interval population with normal outcomes, red blood cell (RBC), hemoglobin (HGB), hematocrit (HCT), and platelet (PLT) values were lower in twin-pregnant women during gestation than in healthy nulligravida women, but the levels of white blood cells (WBC), neutrophils (NEU), and the NEU% increased, especially in the mid-term. The reference intervals of late-term pregnancy were validated using 20 twin pregnancies samples, and then utilized to determine the distinctive CBC characteristics in preterm birth (PTB) pregnancy. Absolute WBC and NEU values increased in PTB pregnancy based on our established reference intervals, which suggests that these may might be prognostic indicators of this adverse outcome. CONCLUSION: Establishing the reference interval of blood cell-related indicators of normal twin pregnancy is helpful for the monitoring and prognosis of gestation.

Fetal oxygen supply can be improved by an effective cross-talk between fetal erythrocytes and vascular endothelium.

In twin/multiple pregnancy, siblings experience an adverse intrauterine environment which forms the major etiological factor leading to pathological conditions. The status of the developing fetus is highly determined by the nitric oxide (NO) level, that facilitates vasodilation which in turn modulates the oxygen and nutrition supply. As the umbilical cord (UC) lacks innervation, activation of the endothelial nitric oxide synthase (NOS3) is fundamental to maintain adequate NO production. Recent ground breaking fact showed that under stress conditions, circulating red blood cells (RBCs) can actively produces NO as a "rescue mechanism". Therefore, this study majorly focused on the molecular mechanisms that affected the redox environment by altering NOS3 activation - both in the UC arteries and vein endothelium and RBCs - that have impacts on developmental parameters, like birth weight. In connection to that, we pursued the communication efficiency between the vessels' endothelium and the circulating RBCs in demand of bioavailable NO. Our results indicated that twinning itself at stage 33-35 weeks, does not reduce the NOS3 level and its phosphorylation status in the cord vessels. However, RBC-NOS3 activation is highly upregulated during this period - providing additional evidence for the active regulatory role of fetal RBCs in the rate of blood flow - and this functional activity highly correlates with the birth weight of the fetuses. Detailed analysis on NOS3 signalling at different time points of gestation could establish a benchmark in understanding of the pathophysiological mechanisms involved in the process of developing neonatal vascular diseases.

Maternal vascular endothelial growth factor receptor and interleukin levels in pregnant women with twin-twin transfusion syndrome.

Twin-twin transfusion syndrome (TTTS) is an unusual and serious condition that occurs in twin pregnancies when identical twins share a placenta but develop discordant amniotic fluid volumes. TTTS is associated with an increased risk of fetal death and birth defects if untreated. This study investigated the soluble levels of biomarkers including growth factors and interleukins in pregnant women with and without TTTS during pregnancy. We quantified plasma levels of VEGF-R1, VEGF-R2, IL-1ß, IL-6 and IL-8 in twin pregnant women with (n=53) and without TTTS (n=72) and in women with single pregnancy (n=30) by ELISA and analyzed the association of maternal circulating biomarker levels with TTTS. Our results showed that maternal VEGF-R1 levels were significantly higher in twins compared to single pregnancy (P<0.05) and were decreased in the second trimester compared to the first trimester (P = 0.065, 0.019 and 0.072 for twins with and without TTTS and single pregnancy, respectively). VEGF-R2 levels had a trend to be lower in twins compared to single pregnancy. In addition, soluble VEGF-R1 and VEGF-R2 levels were significantly decreased while IL-6 levels were increased after surgical treatment with laser in twin pregnant women with TTTS (P = 0.016, 0.041 and 0.04, respectively). These results suggest that IL-6, VEGF-R1 and VEGF-R2 are involved in vascular regulation and stabilization in twin pregnancies and may contribute to the pathogenesis of TTTS and thus play a prognostic role in the surgical treatment of TTTS.

Non-invasive prenatal testing in the management of twin pregnancies.

Twin pregnancies are common and associated with pregnancy complications and adverse outcomes. Prenatal clinical management is intensive and has been hampered by inferior screening and less acceptable invasive testing. For aneuploidy screening, meta-analyses show that non-invasive prenatal testing (NIPT) through analysis of cell-free DNA (cf-DNA) is superior to serum and ultrasound-based tests. The positive predictive value for NIPT is driven strongly by the discriminatory power of the assay and only secondarily by the prior risk. Uncertainties in a priori risks for aneuploidies in twin pregnancies are therefore of lesser importance with NIPT. Additional information on zygosity can be obtained using NIPT. Establishing zygosity can be helpful when chorionicity was not reliably established early in pregnancy or where the there is a concern for one versus two affected fetuses. In dizygotic twin pregnancies, individual fetal fractions can be measured to ensure that both values are satisfactory. Vanishing twins can be identified by NIPT. Although clinical utility of routinely detecting vanishing twins has not yet been demonstrated, there are individual cases where cf-DNA analysis could be helpful in explaining unusual clinical or laboratory observations. We conclude that cf-DNA analysis and ultrasound have synergistic roles in the management of multiple gestational pregnancies.

Fetal loss after chorionic villus sampling in twin pregnancy.

OBJECTIVE: To estimate the chorionic villus sampling (CVS)-related risk of fetal loss in twin pregnancy after adjustment for chorionicity, nuchal translucency thickness (NT), intertwin discordance in crown-rump length (CRL), maternal demographic characteristics and serum pregnancy-associated plasma protein-A (PAPP-A) and free ß-human chorionic gonadotropin (ß-hCG). METHODS: This was a multicenter study from eight fetal medicine units in which the leadership were trained at the Harris Birthright Research Centre for Fetal Medicine in London, UK, and in which the protocols for screening, invasive testing and pregnancy management are similar. Data were obtained prospectively from women with twin pregnancy undergoing routine ultrasound examination at 11-13 weeks' gestation. Multivariable logistic regression analysis with backward stepwise elimination was used to examine whether CVS provided a significant independent contribution to the prediction of risk of fetal loss after adjusting for maternal and pregnancy characteristics, including maternal age, racial origin and weight, method of conception, smoking status, parity, chorionicity, intertwin discordance in CRL, fetal NT ≥ 95th percentile and free ß-hCG and PAPP-A multiples of the median. Similarly, within the CVS group, multivariable logistic regression analysis was used to investigate the effect of the number of intrauterine needle insertions and size of the needle on the risk of fetal loss. RESULTS: The study population of 8581 twin pregnancies undergoing ultrasound examination at 11-13 weeks' gestation included 316 dichorionic and 129 monochorionic twins that had CVS. First, in twin pregnancies undergoing CVS, compared to those not undergoing CVS, there was a 2-fold increased risk of fetal loss at < 24 weeks' gestation and of loss at any stage in pregnancy. Second, the factors providing a significant independent contribution to the prediction of miscarriage or fetal loss in twin pregnancy were increased maternal weight, black racial origin, monochorionicity, and more so monoamnionicity, large intertwin discordance in CRL and increased fetal NT, and, in the case of fetal loss at any stage, there was also a contribution from assisted conception and low serum PAPP-A. Third, after adjustment for maternal and pregnancy characteristics, CVS did not provide a significant contribution to the risk of fetal loss. Fourth, in twin pregnancies that had CVS, there was no significant contribution to fetal loss from the number of intrauterine needle insertions or needle size. CONCLUSION: The 2-fold increased risk of fetal loss following CVS in twin pregnancy can, to a great extent, be explained by maternal and pregnancy characteristics rather than the invasive procedure itself. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

DEVELOPING twin-specific 75-g oral glucose tolerance test diagnostic thresholds for gestational diabetes based on the risk of future maternal diabetes: a population-based cohort study.

OBJECTIVE: To develop twin-specific outcome-based oral glucose tolerance test (OGTT) diagnostic thresholds for GDM based on the risk of future maternal type-2 diabetes. DESIGN: A population-based retrospective cohort study (2007-2017). SETTING: Ontario, Canada. METHODS: Nulliparous women with a live singleton (n = 55 361) or twin (n = 1308) birth who underwent testing for gestational diabetes mellitus (GDM) using a 75-g OGTT in Ontario, Canada (2007-2017). We identified the 75-g OGTT thresholds in twin pregnancies that were associated with similar incidence rates of future type-2 diabetes to those associated with the standard OGTT thresholds in singleton pregnancies. RESULTS: For any given 75-g OGTT value, the incidence rate of future maternal type-2 diabetes was lower for women with a twin than women with a singleton pregnancy. Using women with a negative OGTT as reference, the risk of future maternal type-2 diabetes in twin pregnancies with a positive OGTT based on the standard OGTT thresholds (9.86 per 1000 person years, adjusted hazard ratio (aHR) 4.79, 95% CI 2.69-8.51) was lower than for singleton pregnancies with a positive OGTT (18.74 per 1000 person years, aHR 8.22, 95% CI 7.38-9.16). The twin-specific OGTT fasting, 1-hour and 2-hour thresholds identified in the current study based on correlation with future maternal type-2 diabetes were 5.8 mmol/l (104 mg/dl), 11.8 mmol/l (213 mg/dl) and 10.4 mmol/l (187 mg/dl), respectively. CONCLUSIONS: We identified potential twin-specific OGTT thresholds for GDM that are associated with a similar risk of future type-2 diabetes to that observed in women diagnosed with GDM in singleton pregnancies based on standard OGTT thresholds. TWEETABLE ABSTRACT: Potential twin-specific OGTT thresholds for GDM were identified.

A comparative study of two immunoassays of maternal placental growth factor.

Circulating maternal levels of placental growth factor correlates well with placental function and numerous studies advocate its role to help rule-out preterm pre-eclampsia. A number of automated immunoassay platforms to quantify placental growth factors are currently available. The aim of this study was to highlight the importance of developing and validating appropriate reference ranges and clinical cut-offs for immunoassays, by comparing the results obtained from two different immunoassays of placental growth factor; the Quantikine® ELISA and the automated Triage® test. This was a secondary subgroup analysis of samples collected as part of a prospective cross-sectional study of placental growth factors in twin pregnancy. Consenting pregnant women with a twin pregnancy, across a variety of gestations, had a single blood sample taken at a one-time point only during their pregnancy. The plasma was initially biobanked and then later analysed in batches using both immunoassays. Although the placental growth factor values of the two immunoassays correlated well (r = 0.88, n = 178, p < .001), the actual results obtained were significantly different (mean difference 238.1 pg/ml). Poor concordance between the two immunoassays was also present, with the Triage® test recording 36 cases as <100 pg/ml whereas the Quantikine® ELISA identified only 4 as <100 pg/ml. Biomarker levels may vary significantly between different immunoassay platforms, highlighting the importance of developing validated clinical cut-offs for any automated immunoassay before its clinical application. These differences need to be understood to facilitate clinical utility given that placental growth factor testing is likely to be introduced into widespread clinical practice.

Vitamin D status in women with dichorionic twin pregnancies and their neonates: a pilot study in China.

BACKGROUND: Vitamin D deficiency is a global public health issue in women and children and is associated with adverse impacts on child growth, such as rickets. However, prior studies have mainly focused on measuring vitamin D levels in singleton pregnant women and their offspring, and very limited studies have revealed the prevalence of vitamin D deficiency in twin pregnant women and their offspring. The aim of this study was to investigate vitamin D levels in twin-pregnant women and their neonates. We also explored the correlation of maternal vitamin D levels with neonatal outcomes and infant growth. METHODS: A prospective subcohort investigation was carried out among 72 dichorionic, diamniotic twin-pregnant mothers and their twin offspring from the Longitudinal Twin Study. Peripheral blood was collected from the mothers in the third trimester, and cord blood was collected from neonates at birth to identify 25[OH]D levels. Data on the characteristics of the mothers and neonates were collected. Infant growth data and food sensitivities were also collected. RESULTS: The average maternal 25[OH]D level was 31.78 ng/mL, with 19.4% being deficient and 20.8% insufficient, while the average neonatal 25[OH]D level was 15.37 ng/mL, with 99.3% being deficiency or insufficient. A positive correlation was found between maternal and neonatal 25[OH]D levels (beta-value: 0.43, 95% CI: 0.37, 0.49). Interestingly, the higher the maternal 25[OH]D level was, the smaller the cotwin birthweight discordance (beta-value: -2.67, 95% CI: - 5.11, - 0.23). In addition, the infants of mothers with vitamin D deficiency were more likely to be allergic to foods at 6 months than those of mothers with vitamin D sufficiency. CONCLUSIONS: Twin neonates were at high risk of vitamin D deficiency, although their mothers' vitamin D deficiency partially improved. Higher maternal vitamin D levels were associated with smaller discordance of cotwin birthweight. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR-OOC-16008203 , 1st April 2016.

Prediction of adverse perinatal outcome and the mean time until delivery in twin pregnancies with suspected pre-eclampsia using sFlt-1/PIGF ratio.

PURPOSE: An elevated soluble fms-like tyrosine kinase-1 (sFlt-1) / placental growth factor (PlGF) ratio is associated with adverse perinatal outcome (APO) and the mean time until delivery (MTUD) in singleton pregnancies complicated by pre-eclampsia (PE). Data on APO and MTUD prediction in twin pregnancies using sFlt-1/PlGF ratio are scarce. We evaluated the predictive value of the sFlt-1/PIGF ratio regarding APO and MTUD in twin pregnancies with suspected PE and/or HELLP syndrome. METHODS: This is a single center retrospective cohort study. All twin pregnancies with suspected PE/HELLP and determined sFlt-1/PIGF were included. Composite APO (CAPO) was defined as the presence of at least one of the following outcomes: respiratory distress syndrome (RDS), intubation, admission to neonatal intensive care unit (NICU) and arterial umbilical cord pH value < 7.10. Selective fetal growth restriction (s-FGR) was analyzed separately. RESULTS: For final analysis, 49 twin pregnancies were included. Median sFlt-1/PIGF ratio was not significantly different in patients with CAPO compared to those without (89.45 vs. 62.00, p = 0.669). MTUD was significantly negative correlated with sFlt-1/PIGF ratio (r = -0.409, p < 0.001). For the whole study cohort, ROC analysis revealed no predictive value for sFlt-1/PIGF and CAPO (AUC = 0.618, 95% CI: 0.387-0.849, p = 0.254). However, sFlt-1/PIGF ratio showed a predictive value for s-FGR (AUC = 0.755, 95% CI: 0.545-0.965, p = 0.032). CONCLUSION: In twin pregnancies with PE and/or HELLP, sFlt-1/PIGF ratio may be helpful for s-FGR prediction and decision-making regarding close monitoring of high-risk patients. However, further prospective studies are warranted to define the role of sFlt-1/PlGF ratio as outcome predictor in twin pregnancies.

Temporal persistence of residual fetal cell-free DNA from a deceased cotwin after selective fetal reduction in dichorionic diamniotic twin pregnancies.

OBJECTIVES: To determine the temporal persistence of the residual cell-free DNA (cfDNA) of the deceased cotwin in maternal circulation after selective fetal reduction and evaluate its long persistence in noninvasive prenatal testing (NIPT). METHODS: Dichorionic diamniotic twins (N = 5) undergoing selective fetal reduction because of a trisomy were recruited. After informed consent, maternal blood was collected immediately before reduction and periodically after reduction until birth. The plasma cfDNA of each sample was sequenced and analyzed for fetal aneuploidy and fetal fractions. RESULTS: In all pregnancies, the fetal fraction of the cfDNA of the deceased fetus increased to peak at 7-9 weeks after fetal reduction, and subsequently decreased gradually to almost undetectable during the late third trimester. The NIPT T-scores persistently reflected the detection of fetal trisomy up to 16 (median 9.5) weeks after fetal reduction. CONCLUSIONS: Residual cfDNA from the deceased cotwin after selective reduction at 14-17 gestational weeks led to the persistent generation of false-positive NIPT results for up to 16 weeks postdemise. Thus, providing NIPT for pregnancies with a cotwin demise in early second trimester is prone to misleading results and not recommended.

Should vanishing twin pregnancies be systematically excluded from cell-free fetal DNA testing?

OBJECTIVE: To demonstrate the feasibility of cell-free DNA (cfDNA) testing in vanishing twin (VT) pregnancies in routine clinical practice. METHODS: Our study included 24 874 singleton and 206 VT consecutive pregnancies. Cell-free DNA was analyzed by massively parallel sequencing. Both aneuploidy analysis (chromosomes 13,18, 21, X, and Y) and fetal fraction estimation were performed according to an Illumina algorithm. Contaminant DNA contribution from the demised co-twin was studied in detail. RESULTS: VT pregnancies exhibited a higher prevalence of screen-positive cases (5.8% vs 2.5%), sex discrepancies (10.2% vs 0.05%), and false positive rates (FPR) (2.6% vs 0.3%) than singleton pregnancies. However, their incidence was significantly lower in tests performed after the 14th week (screen-positive cases: 3.1%; sex discrepancies: 7.8%; and FPR: 0.8%). Among the 12 cases in which cfDNA was performed at two time points, fading of contaminating cfDNA was observed in four cases with a sex discrepancy and in one false positive for trisomy 18, resulting in a final correct result. CONCLUSIONS: Our data suggest VT pregnancies could be included in cfDNA testing as long as it is applied after the 14th week of pregnancy. However, future studies to validate our findings are needed before including VT cases in routine clinical practice. Once established, unnecessary invasive procedures could be avoided, mitigating negative emotional impact on future mothers.

Chimerism involving a RB1 pathogenic variant in monochorionic dizygotic twins with twin-twin transfusion syndrome.

We report the first case of blood chimerism involving a pathogenic RB1 variant in naturally conceived monochorionic-dizygotic twins (MC/DZ) with the twin-twin-transfusion syndrome (TTTS), presumably caused by the exchange of stem-cells. Twin A developed bilateral retinoblastoma at 7 months of age. Initial genetic testing identified a de novo RB1 pathogenic variant, with a 20% allelic ratio in both twins' blood. Subsequent genotyping of blood and skin confirmed dizygosity, with the affected twin harboring the RB1 pathogenic variant in skin and blood, and the unaffected twin carrying the variant only in blood.

Thyroid Function Test Abnormalities in Twin Pregnancies.

Background: Compared with singletons, a twin pregnancy is associated with a larger thyroid hormone demand and an increased stimulation of gestational thyroid function due to higher concentrations of human chorionic gonadotropin. However, such effects have been sparsely quantified. The aim of this study was to evaluate thyroid function and thyroid function test abnormalities in twin pregnancies during early and late pregnancy compared with singletons. Methods: We included 1208 twin pregnancies and 46,834 singleton pregnancies with thyroid function tests available. Thyroid function test abnormalities were defined using population-based reference ranges. The analyses were adjusted for potential confounders including maternal age and body mass index. Results: Compared with singletons, a twin pregnancy was associated with a lower thyrotropin (TSH) (ß = -0.46 [95% confidence interval, CI -0.49 to -0.44], p < 0.001) and a higher free thyroxine (fT4) (ß = 0.91 [CI 0.69-1.16], p < 0.001) during early pregnancy. During late pregnancy, a twin pregnancy was associated with a higher TSH (ß = 0.35 [CI 0.29-0.42], p < 0.001) while fT4 did not differ (ß = -0.11 [CI -0.22 to 0.01], p = 0.065). During early pregnancy, a twin pregnancy was associated with a higher risk of overt hyperthyroidism (odds ratio, OR = 7.49 [CI 6.02-9.33], p < 0.001), subclinical hyperthyroidism (OR = 5.26 [CI 4.17-6.64], p < 0.001), and isolated hypothyroxinemia (OR = 1.89 [CI 1.43-2.49], p < 0.001), but with a lower risk of subclinical hypothyroidism (OR = 0.27 [CI 0.13-0.54], p < 0.001). In late pregnancy, a twin pregnancy was associated with a higher risk of subclinical hypothyroidism (OR = 4.05 [CI 3.21-5.11], p < 0.001), isolated hypothyroxinemia (OR = 1.48 [CI 1.04-2.10], p = 0.028), and subclinical hyperthyroidism (OR = 1.76 [CI 1.27-2.43], p < 0.001). Conclusions: During early pregnancy, a twin pregnancy was associated with a higher thyroid function and a higher risk of (subclinical) hyperthyroidism, as well as a higher risk of isolated hypothyroxinemia. During late pregnancy, a twin pregnancy was associated with a higher TSH concentration and a higher risk of subclinical hypothyroidism, as well as a persistently higher risk of isolated hypothyroxinemia and subclinical hyperthyroidism. The study was approved by Chinese Clinical Trial Registry (registration no. ChiCTR1800014394).

Perinatal outcomes of twin pregnancies complicated by late twin-twin transfusion syndrome: A systematic review and meta-analysis.

INTRODUCTION: Untreated twin-to-twin transfusion syndrome (TTTS) is associated with a high risk of perinatal mortality and morbidity. Laser surgery is recommended before 26 weeks of gestation. However, the optimal management in case of late TTTS (occurring after 26 weeks of gestation) is yet to be established. MATERIAL AND METHODS: We conducted a systematic review and meta-analysis to evaluate the outcomes of monochorionic-diamniotic twin pregnancies complicated by late TTTS according to different management options (expectant, laser therapy, amnioreduction, or delivery). The primary outcome was mortality, including single and double intrauterine, neonatal, and perinatal death. Secondary outcomes were composite morbidity, neuromorbidity, respiratory distress syndrome, admission to neonatal intensive care unit, intact survival (ie, free from neurological complications), and preterm birth before <32 weeks of gestation. Outcomes were reviewed according to the management and reported for the overall population of twins and disease status (ie, donor and recipient separately). Random-effect meta-analyses of proportions were used to analyze the data. RESULTS: Nine studies including 796 twin pregnancies affected by TTTS were included. No randomized controlled trials were available for inclusion. TTTS occurred at ≥26 weeks of gestation in 8.7% (95% CI 6.9%-10.9%; 67/769) of cases reporting TTTS at all gestations. Intrauterine death occurred in 17.7% (95% CI 4.9%-36.2%) of pregnancies managed expectantly, 5.3% (95% CI 0.9%-12.9%) of pregnancies treated with laser, and 0% (95% CI 0%-9%) after amnioreduction. Neonatal death occurred in 42.5% (95% CI 17.5%-69.7%) of pregnancies managed expectantly, in 2.8% (95% CI 0.3%-7.7%) of cases treated with laser, and in 20.2% (95% CI 6%-40%) after amnioreduction. Only one study (10 cases) reported data on immediate delivery after diagnosis with no perinatal deaths. Perinatal death incidence was 55.7% (95% CI 31.4%-78.6%) in twin pregnancies managed expectantly, 5.6% (95% CI 0.5%-15.3%) in those treated with laser, and 20.2% (95% CI 6%-40%) in those after amnioreduction. Intact survival was reported in 44.4%, 96.4%, and 78% of fetuses managed expectantly, with laser or amnioreduction, respectively. CONCLUSIONS: Evidence regarding perinatal mortality and morbidity in twin pregnancies complicated by late TTTS according to the different managements was of very low quality. Therefore further high-quality research in this field is needed to elucidate the optimal management of these pregnancies.